Formamide is one of the important compounds from which prebiotic molecules can be synthesized, provided that its concentration is sufficiently high. For nucleotides and short DNA strands, it has been shown that a high degree of accumulation in hydrothermal pores occurs, so that temperature gradients might play a role in the origin of life [Baaske P, et al. (2007) Proc Natl Acad Sci USA 104(22): 9346−9351]. We show that the same combination of thermophoresis and convection in hydrothermal pores leads to accumulation of formamide up to concentrations where nucleobases are formed. The thermophoretic properties of aqueous formamide solutions are studied by means of Infrared Thermal Diffusion Forced Rayleigh Scattering. These data are used in numerical finite element calculations in hydrothermal pores for various initial concentrations, ambient temperatures, and pore sizes. The high degree of formamide accumulation is due to an unusual temperature and concentration dependence of the thermophoretic behavior of formamide. The accumulation fold in part of the pores increases strongly with increasing aspect ratio of the pores, and saturates to highly concentrated aqueous formamide solutions of ∼85 wt% at large aspect ratios. Time-dependent studies show that these high concentrations are reached after 45-90 d, starting with an initial formamide weight fraction of 10 −3 wt % that is typical for concentrations in shallow lakes on early Earth.concentration problem | hydrothermal vents | molecular evolution | origin-of-life problem | thermophoresis T hermophoresis has been suggested as an active transport mechanism to reach high concentrations of prebiotic molecules to culminate in the formation of RNA (1). A still open question is whether thermophoresis can also be a possible mechanism to form prebiotic nucleobases from simple molecules such as hydrogen cyanide (HCN) and formamide (FA). Already for almost 50 years, FA has been discussed as an important compound from which prebiotic molecules originate (2-7). It has been shown that all known nucleobases can be synthesized from aqueous FA solutions (4). In diluted HCN solutions, polymerization of HCN to form nucleobases becomes favored over hydrolysis of HCN at concentrations of 0.03-0.3 wt % (8). To our knowledge, there are no similar studies of diluted FA solutions. Taking into account the faster hydrolysis of FA (3), we estimated that a 100-timeshigher concentration between 3 wt % and 33 wt % should be sufficient for the synthesis of prebiotic molecules in aqueous solutions. In the ocean during the early stages of Earth, the natural occurring concentrations at a low temperature (10°C) and a pH between 6 and 8 are estimated to be only on the order of 10 −9 wt %, whereas, in shallow lakes (depth 10 m), due to vaporization and FA input from the atmosphere, higher concentrations of about 10 −3 wt % are possible (3). Still, these natural concentrations are far too small compared with those required for the formation of nucleobases.In this work, we perform numerical calculations ...

Neuromuscular interfaces are required to translate bioelectronic technologies for application in clinical medicine. Here, by leveraging the robotically controlled ink-jet deposition of low-viscosity conductive inks, extrusion of insulating silicone pastes, and in situ activation of electrode surfaces via cold-air plasma, we show that soft biocompatible materials can be rapidly printed for the on-demand prototyping of customized electrode arrays well-adjusted to specific anatomical environments, functions and experimental models. We also show that the printed bioelectronic interfaces allow for long-term integration and functional stability, for the monitoring and activation of neuronal pathways in the brain, spinal cord and neuromuscular system of cats, rats and zebrafish. The technology might enable personalized bioelectronics for neuroprosthetic applications. One-sentence editorial summary:Customized soft electrode arrays well-adjusted to specific anatomical environments, functions and experimental models can be rapidly prototyped via the robotically controlled deposition of conductive inks and insulating inks.

We study the thermodiffusion behavior of spherical polystyrene beads with a diameter of 25 nm by infrared thermal diffusion Forced Rayleigh Scattering (IR-TDFRS). Similar beads were used to investigate the radial dependence of the Soret coefficient by different authors. While Duhr and Braun (Proc. Natl. Acad. Sci. U.S.A. 104, 9346 (2007)) observed a quadratic radial dependence Braibanti et al. (Phys. Rev. Lett. 100, 108303 (2008)) found a linear radial dependence of the Soret coefficient. We demonstrated that special care needs to be taken to obtain reliable thermophoretic data, because the measurements are very sensitive to surface properties. The colloidal particles were characterized by transmission electron microscopy and dynamic light scattering (DLS) experiments were performed. We carried out systematic thermophoretic measurements as a function of temperature, buffer and surfactant concentration. The temperature dependence was analyzed using an empirical formula. To describe the Debye length dependence we used a theoretical model by Dhont. The resulting surface charge density is in agreement with previous literature results. Finally, we analyze the dependence of the Soret coefficient on the concentration of the anionic surfactant sodium dodecyl sulfate (SDS), applying an empirical thermodynamic approach accounting for chemical contributions.

The supported lipid bilayer (SLB) is a well-known system for studying the cell membrane and membrane proteins. It is also promising as a platform for studying cell processes: the cell adhesion, the cell membrane receptors, and the intercellular signaling processes. SLBs made of natural lipids appeared to be protein and cell repellent. Thus, to use the SLB as a substrate for cells, one should functionalize them to provide adhesion. In the present paper, we describe a simple approach to promote adhesion of neuronal cells to the SLB without using proteins or peptides, by introducing positively charged lipids 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP) into the SLB made of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC). We show that neurons adhere to these bilayers and grow for at least 10 days. The SLBs themselves were found to degrade with time in cell culture conditions, but maintained fluidity (as revealed by fluorescence recovery after photobleaching), demonstrating the possibility of using SLBs for studying neuronal cells in culture.